The diversity tree developed as part of the global conservation strategy for the conservation and use of eggplant genetic resources is now available in Genesys.
A “diversity tree” is a representation of the overall structure of a crop genepool obtained by classifying its diversity in a hierarchical manner, based on information from the literature and expert opinion. The original idea was proposed by Van Treuren et al. (2009). A diversity tree for the eggplant genepool has been prepared as part of the process of developing the global conservation strategy for the conservation and use of eggplant genetic resources, and can be consulted on Genesys.
Using data from Genesys and WIEWS (World Information and Early Warning System on Plant Genetic Resources for Food and Agriculture), Svein Solberg, the first author on the eggplant strategy, and Peter Giovannini, who coordinates the development of crop strategies at the Crop Trust, estimated the number of accessions in each end-group in the eggplant diversity tree, and identified groups that are not well represented.
This analysis highlighted in particular that some crop wild relative species are not well represented in ex situ collections and that a high proportion of accessions in the eggplant genepool have an unknown or undefined “biological type” in Genesys and WIEWS. That means we do not know whether they are landraces, old varieties, or even wild species.
The primary division into Old World, New World, and Australian species is based on molecular marker research (Weese and Bohs, 2010; Stern et al., 2011; Knapp et al., 2013). But the taxonomy is challenging. The Old World group can be further divided into the Eggplant clade, the Anguivi clade, and “Others”. The Eggplant clade includes brinjal eggplant and its closest wild ancestor, Solanum insanum L. plus nine other wild species (Syfert et al., 2016). The Anguivi clade includes two other cultivated species -- scarlet eggplant (Solanum aethiopicum) and gboma eggplant (Solanum macrocarpon) -- and more than 30 wild species (Lester and Daunay, 2003; Lester et al., 2011). The third clade includes another 30 wild species, of which 7 are highlighted as eggplant wild relatives.
In contrast to other important crops, cultivated Solanum melongena lacks molecular studies including a large number of accessions (see for example Tripodi et al., 2021 for peppers). However, there is evidence of distinct occidental (Europe, Africa and America ) and oriental clusters (Asia) (Vilanova et al., 2021, Cericola et al., 2013), and to a lesser extent of morphological and molecular differentiation at the level of the country of origin (Hurtado et al 2012).
Asia is the center of domestication and the primary center of diversity, therefore this region was further divided into subclusters to differentiate countries where high diversity is found, such as India and China. For cultivated Solanum aethiopicum, a differentiation into four cultivar groups is based on fruit and leaf morphology: gilo, kumba, aculeatum, and shum. (Lester and Niakan, 1986; Prohens et al., 2012). Solanum macrocarpon has no recognized cultivar groups.
This article was provided to Genesys by Svein Solberg, the first author on the eggplant strategy, and Peter Giovannini, who coordinates the development of crop strategies at the Crop Trust, and Luigi Guarino, Director of Science at The Global Crop Diversity Trust.
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